This application relates to preventing, controlling reducing and/or treating proliferative vitreoretinopathy. Proliferative vitreoretinopathy (including epiretinal membrane formation) is a potentially devastating ophthalmic condition that can lead to blindness. It can develop after any penetration of the eyexe2x80x94surgical or traumatic. Predisposing conditions therefore include, but are not limited to, penetrating trauma, retinal tears, traction detachments, vitrectomy, and intraocular surgery. Any ophthalmic condition that precipitates or permits migration of retinal pigment is epithelium or glial cells can lead to the development of proliferative vitreoretinopathy. See Machamer (1978) British J. Ophthal. 62:737; Hilton et al. (1983) Ophthalmology 90:121.
I have discovered that glutamate causes migration and proliferation of retinal pigment epithelium and/or glial cells. The invention features the use of glutamate antagonists to reduce or control retinal pigment epithelium and/or glial migration and the subsequent development of proliferative vitreoretinopathy. Avoidance or management of proliferative vitreoretinopathy can be achieved by administering to the patient a compound capable of reducing glutamate-induced retinal pigment epithelium and/or glial migration in a concentration effective to reduce such migration.
While I do not wish to be bound to any specific theory, I conclude that one or more of the several types of calcium-permeable CNS ion channels mentioned below can be involved in controlling such migration, including: a) the various aspects of the NMDA (N-methyl-D-aspartate) receptor channel complex; b) the voltage-dependent Ca2+channels; and c) other channels directly coupled to glutamate (or excitatory amino acid) receptors. Such channels are reviewed in: Sommer, B. and Seeburg, P. H. xe2x80x9cGlutamate receptor channels: novel properties and new clonesxe2x80x9d Trends Pharmacological Sciences 13:291-296 (1992); Nakanishi, S., xe2x80x9cMolecular Diversity of glutamate receptors and implications for brain functionxe2x80x9d, Science 248:597-603 (1992).
One aspect of the invention generally features a method of treating, preventing, or reducing proliferative vitreoretinopathy in a patient by administering to the patient""s retina an effective amount of a compound that reduces CNS neuronal damage incident to (associated with) calcium ion influx.
A second aspect of the invention features treating, preventing, or reducing proliferative vitreoretinopathy in a patient by administering to the patient""s retina an effective amount of at least one of the compounds listed in one or more of Tables 2-5. below.
A third aspect of the invention features treating preventing or reducing proliferative vitreoretinopathy in a patient by administering to the patient""s retina an effective amount of a compound that reduces glutamate related retinal cell migration, proliferation, or both.
The compound may be one of the so-called NMDA antagonistsxe2x80x94i.e., it reduces neuronal damage mediated by the NMDA receptor complex. Alternatively, the compound antagonizes neuronal damage mediated by the voltage-dependent calcium channel. Other useful compounds are those which limit release of glutamate from cells or reduce the intracellular neurotoxic consequences of glutamate interaction with cell membrane glutamate receptors. Preferably, the compound crosses the blood-retinal barrier.
The patient may be anyone who has experienced, or is at risk for experiencing, penetrating trauma, retinal tear, traction detachment, vitrectomy, or intraocular surgery. The compound may be administered to the patient topically, orally, or intravitreally, as well as by other routes described below. It may be administered chronically, i.e., over an extended period of a month or even six months or years.
The invention preferably will be used to treat patients having proliferative vitreoretinopathy or to treat patients prophylactically to avoid that condition. Preferably, the agent is administered over an extended period (e.g., at least six months and preferably at least one year). Those at risk for developing proliferative vitreoretinopathy include patients who have experienced penetrating trauma, retinal tears, traction detachments, vitrectomy, or intraocular surgery.
Particularly preferred compounds are antagonists of the NMDA receptor-channel complex. The term xe2x80x9cNMDA receptor antagonistsxe2x80x9d includes several sub-types of NMDA antagonists including: a) channel blockersxe2x80x94i.e., antagonists that operate uncompetitively to block the NMDA receptor channel; b) receptor antagonistsxe2x80x94antagonists that compete with NMDA to act at the NMDA binding site; c) agents acting at either the glycine co-agonist site or any of several modulation sites such as the zinc site, the magnesium site, the redox modulatory site, or the polyamine site; d) agents which inhibit the downstream effects of NMDA receptor stimulation, such as agents that inhibit activation of protein kinase C activation by NMDA stimulation, antioxidants, and agents that decrease phosphatidylinositol metabolism.
Other compounds that are useful in the invention include voltage-dependent calcium channel antagonists, e.g. those which exert a substantial direct effect on glutamate toxicity mediated by the L-type voltage dependent Ca++ channel in that they produce a statistically significant result in experiments measuring glutamate induced effects by the general method described in Karschian and Lipton, J. Physiol. 418: 379-396 (1989) or by other techniques for measuring antagonism of the L-type Ca++ channel known to those in the art. (We contrast the direct effect so measured with the secondary effects of excitoxicity mediated by other channels, which in turn causes flow through the voltage dependent Ca++ channels.) Particular candidate compounds include Class I voltage dependent Ca++ channel antagonists, e.g., phenylalkylamines.
Preferably, the compounds used cross the blood-retina barrier and can be administered chronically. Other useful agents act as antagonists of non-NMDA receptors (glutamate receptor types other than the NMDA receptor complex discussed above), and include agents which block inotropic glutamate receptors or interact with metabotropic glutamate receptors (Nakanishi, supra). Still other agents act to limit (reduce) release of glutamate from cells, thereby acting upstream from the glutamate receptors in the excitatory neurotoxicity process. Still other agents may act by blocking downstream effects of glutamate receptor stimulation, e.g., the intracellular consequences of glutamate interaction with a cell membrane glutamate receptor, such as agents (like dantrolene) that block the rise in intracellular calcium following stimulation of membrane glutamate receptors.
The most preferred compounds are those capable of crossing the blood-retinal barrier; these compounds may be administered orally, intravenously, or topically and cross intervening barriers including the blood-retina barrier to reach the retinal ganglion cells. Compounds that do not freely cross the blood-retina barrier are less preferred; these compounds may be administered intravitreally to the retina. In the case of compounds that have an intermediate ability to cross the blood-retina barrier, the mode of administration will depend on the dosage required and other factors.
Among the preferred compounds are amantadine derivatives (e.g., memantine, amantadine, and rimantadine), nitroglycerin, dextorphan, dextromethorphan, and CGS-19755. See generally, the compounds listed in Table 2.
The invention is useful for the reduction or prevention (including prophylactic treatment) of damage as a result of proliferative vitreoretinopathy.